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The Vagus Nerve
Bob Caruthers, CST, PLD
Auricular branch to posterior part of aur~cleand
part of external meatus
'NTRODUCTlON
NERVaiS
There are 12 pairs of cranial nerves.
They are commonly referred to by name
or by number. Two of the 12 pair, the
olfactory peduncle and the optic nerve,
are not true nerves but neural fiber
Nucleus of sol~tarytract
Nucleus of sp~naltract of V
Levator veh palatin1 muscle
Amb~guousnucleus
Dorsal motor nucleus
Glossopalatinus muscle
Salpingopharyngeus
Pharyngeal constrictors
tracts. The spinal accessory nerve is partially derived from the upper cervical
Sternocle~domastoid
segments of the spinal cord. The nine
Epiglott~cand hngual ram1
other pair are directly related to the
brainstem-midbrain,
pons or medulla.
Typically, the cranial nerve is related to
Interior pharyngeal constrictor
Cr~cothyro~d
muscle
the brain stem level at which the nerve
R~ghtsubclav~anartery
emerges from or enters the brain stem.
R~ghtrecurrent laryngeal nerve
The efferent motor fibers of the cranial
nerves arise from groups of motor nuclei
Right pulmonary plexus
lying deep within the brain stem. These
motor nuclei are homologs to the anterior horn cells of the spinal cord. The
afferent sensory fibers of the cranial
nerves find their cells of origin outside
the brain stem. The cells of origin are
typically ganglia that are homologs to
the dorsal root ganglia of the spinal
nerves. In this case, secondary sensory
allt-
nuclei lie within the brain stem. The
--Motor
cranial nerves with parasympathetic
Sensory nerves
Parasympathet~cnerves
nerves
function are the oculomotor, facial,
glossopharyngeal and v a g u ~ . ~ , ~ , ~
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Tho Surgical Technologlet
FIGURE I-The
components of the functional anatomy of the vagus nerve are complex.
Other components of the functional anatomy of the vagus
nerve are equally complex (Figure 1). Through the pharyngeal
plexus, the levator veli palantini, musculus uvulae, pharyngopalatinus, and glossopalatinus, salpingopharyngeus and pharyngeal constrictors are innervated. The glottis, epiglottic and
lingual rami, inferior pharyngeal constrictor and cricothyroid
muscle are reached by fibers traveling in the superior laryngeal
nerve. The recurrent laryngeal nerve supplies the arytenoid,
thyroarytenoid, lateral cricoarytenoid, and posterior cricoarytenoid muscles and the esophagus. Other branches of the
vagus nerve innervate the heart, pulmonary plexus,
esophageal ~lexus,cardiac plexus, diaphragm, celiac plexus,
stomach, liver, gall bladder, spleen, pancreas and small intesvisceral afferent fibers. A lateral portion is found along the
lateral edge of the solitary fasciculus. Cells from the medial
portion extend rostrally and join the corresponding cell col-
CLINICAL CORRELATIONS
lum on the opposite side to form the commissural nucleus of
Lesions of the vagus nerve may be found intramedullary or
the vagus nerve. The lateral portion surrounds and parallels
peripheral. Lesions affecting the vagus nerve that lie near
the solitary fasciculus. The cells are more prominent in their
the base of the skull often involve the glossopharyngeal and
rostral projection and this enlarged rostral portion of the soli-
spinal accessory nerves and may involve the hypoglossal
tary nucleus is the recipient of special visceral afferents related
nerve. A unilateral lesion of the vagus nerve produces ipsi-
to t a ~ t e . ' ' ~ ' ~ ' ~
lateral paralysis of the soft palate, pharynx and larynx. This
Branchial fibers arise from the ambiguous nucleus, which
paralysis produces hoarseness of voice, dyspnea (difficulty
contributes fibers to the cranial component of the spinal
breathing) and dysphagia (difficulty swallowing). Bilateral
accessory nerve, also. These fibers in the spinal accessory
lesions constitute an emergency situation. Bilateral lesions
nerve exit the skull with the spinal accessory but rejoin the
produces complete paralysis of the pharynx and larynx.
vagus nerve outside the skull via the recurrent laryngeal
Death, secondary to asphyxia, is imminent unless an emer-
nerve. The branchial efferent fibers innervate the muscles of
gency tracheostomy is performed. Bilateral lesions also pro-
the soft palate, pharynx and, with the fibers from the spinal
duce paralysis atonia of the esophagus and stomach,
accessory, the intrinsic muscles of the larynx. Visceral efferent
increased and irregular heart rate, and severe dysphagia and
fibers pass to the thoracic and abdominal viscera. These path-
dysarthria (disturbance of articulation of ~ p e e c h ) . ' , ~ , ~
ways have postganglionic fibers arising from terminal ganglia
that lie in or near the viscera innervated. Unipolar cells from
the superior ganglion send fibers via the auricular branch of
the vagus nerve to the external auditory meatus and portions
of the earlobe and via the meningeal branch to the dura of
the posterior fossa. Central branches travel with the vagus
nerve to the brainstem and terminate in the spinal tract of
the trigeminal nerve and its corresponding nucleus. Unipolar
cells of the inferior ganglion send visceral afferent fibers to
the pharynx, larynx, trachea, esophagus, and thoracic and
abdominal viscera. A few special sensory fibers innervate the
BIBLIOGRAPHY
1. Carpenter, MB. Core Text of Neuroanatomy, Pdedition. Williams and
Wilkins: Baltimore, MD, 1978.
2. DeGroot, J. Correlative Neuroanatomy, 21" edition. Appleton & Lange:
Nonvalk, CT, 1991.
3. Guyton, AC. Textbook of Medical Physiology, Phedition. WB Saunders Co.:
Philadelphia, PA, 1991.
4. Purves, D, Augustine, GJ, Fitzpatrick, D, Katz, LC, LaMancia, AS and
McNamara, 10.Neuroscience. Sinauer Associates, Inc, Pub: Sunderland,
MA, 1997.
5. Snyder M. A Guide to Neurological and Neurosurgical Nursing, 2nd edition.
Delmar Publishers Inc: Albany, NY 1991.
6. Wingard LB, Brody, TM, Larner,J and Schwartz, A. Human Pharmacology:
Molecular-to-clinical.Mosby Year Book: St. Louis, MO, 1991.
epiglottis and travel through the inferior ganglion to the gustatory nucleus of the brain tern.',^,^,^
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The Surgical Technologist
F e b r u a r y 1999
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